1. Field of the Invention
The field of the invention generally relates to hydroelectric power generation. In particular, the field of the invention relates to an undershot impulse-jet driven water wheel for placement in a water course such as an irrigation canal or navigable river, without the need for a dam, wherein the water wheel assembly comprises an automatically adjustable radial gate and hinged upper flap to maximize the hydraulic head and optimize the shape of a rectangular shaped jet and to actively maintain the upstream water level within defined limits at any predetermined elevation, that is constrained only by the height of the banks upstream of the installation.
2. Background of Related Art
Conventional waterwheels for generation of electric power contain a speed-increaser gear unit and an electric generator either internally contained within the waterwheel or mounted on a platform located above the waterwheel. Such waterwheel-driven generating units are disclosed in the inventor's own U.S. Pat. No. 5,440,175, entitled “Waterwheel-Driven Generating Unit,” issued Aug. 8, 1995 and in U.S. Pat. No. 6,208,037, “Waterwheel-Driven Generating Assembly,” issued Mar. 27, 2001, both of which are incorporated herein by reference.
Generation of electricity at very low-head dams (less than about 15 feet difference between water levels upstream and downstream of a dam) has become uncompetitive with other forms of electric power generation. This is due to a lack of suitable equipment that can be installed for a total capital cost lower than that of other forms of generation from renewable sources, such as wind power, wave power and solar energy that have no fuel costs. With no hydro generating equipment designed specifically for very low-head sites, the typical approach until now has been to adapt the same types of hydro turbine used at higher-head sites to the lower head sites.
There have been two problems with this approach however. First, the volume of water required to develop the same power output increases inversely to the reduction in head, thereby requiring larger diameter equipment and greater amounts of excavation and concrete for the water passages, all at progressively higher cost for diminishing revenue. Secondly, the proportions of cost required to construct the civil works actually increases faster than the cost of the equipment.
Consequently, what is needed is a more cost-effective waterwheel-driven generating unit characterized by installation costs reduced to the absolute minimum and wherein power-generating equipment is designed for ease of shop fabrication, pre-assembly and transportation at minimal expense.
Impulse-jet turbines of the Pelton or Turgo type using jets of circular cross-section have been used for many years to generate electricity at locations where the available hydraulic head is greater than about 15 meters (about 50 feet). According to the “Guide to Hydropower Mechanical Design” prepared by the American Society of Mechanical Engineers Hydro Power Technical Committee, sites having lower heads were considered more suitable for hydro development using reaction turbines of the Kaplan or propeller type, based on relative efficiencies and the economics of equipment and installation costs. As previously mentioned, however, at very low heads, the cost of both equipment and the civil works needed for conveying water to and from the equipment increases disproportionately in comparison to the value of power produced.
Using presently available equipment and installation methods results in the cost of power becoming uncompetitive at hydraulic head differences less than about 15 feet. Therefore, what is needed is an undershot impulse-jet type of waterwheel designed to maximize the energy obtainable from a given volume of discharge and hydraulic head by utilizing the potential pressure and volume of a rectangular jet impinging on vanes at the bottom of their travel rather than using mainly a gravity effect of a conventional overshot waterwheel, or the kinetic energy in a flowing stream that has traditionally been used to drive the reaction type of undershot waterwheels. The higher velocity of the jet facilitates a greater volume of discharge and rate of rotation with consequent higher power output than either a gravity-driven overshot wheel or a reaction type of undershot waterwheel can develop from the same head and flow.
Up to now, conventional low head hydro generation systems have been inefficient power sources, and are not competitive with other forms of non-fuel based energy production such as wind, wave or solar power. Conventional low-head hydro equipment systems focus on increasing efficiency, resulting in increased manufacturing and installation costs. Efficiency is not the economic key to success. Rather, the key to competitive success for low-head hydropower is to minimize the cost of investment per kilowatt-hour of production. Therefore, what is needed is a low-head hydro generation system and method that maximizes kilowatt-hour production while minimizing investment in component cost and installation. Furthermore, the diameter and consequently the cost of an impulse-jet driven undershot waterwheel can be much less than that of an overshot waterwheel designed to develop power from a particular head since the diameter of the impulse-jet waterwheel can be much less than the available head.